1. Field of the Invention
The present invention pertains to a method and system for replacing mine tailings and similar materials in abandoned mineworks.
2. Background
Certain particulate materials such as mine tailings and other earth materials which have been processed and disposed of may present certain environmental hazards if left to reside on the earth's surface in so-called tailings piles, ponds and other repositories which are exposed to wind and rain. In certain areas mine tailings and the residue of related earth material processing operations may also be found disposed alongside rivers or similar bodies of water or in conventional disposal pits or ponds.
Moving these materials may involve costly dewatering, excavating, drying and storage operations, including material conversion techniques which are or can be in themselves environmentally injurious. On the other hand mine tailings and the residue of other processing operations on earth materials and minerals produce particulate material which is suited to implementation of techniques that utilize mechanical or hydraulic disaggregation, suspension and pumping. For example, mine tailings disposed in piles, pits or ponds may be well suited to dredging operations, slurrification, pumping and transport by pipeline. Excavation of these materials using conventional dredging and pumping techniques can be carried out without contaminating groundwater in adjacent areas. Moreover, certain mine tailings and the residue of ore body processing operations may, when mixed with a cementitious material, form a suitable hardable composition which may, at least, be used as a filler or plugging material and may have certain structural applications. Moreover, hardened cementitious mixtures or grouts may be capable of neutralizing residual acidic components in the tailings and provide physical stability of these materials.
A related problem in dealing with abandoned mine sites pertains to handling groundwaters which accumulate in and leak through mine shafts, drifts and adits. Such sites may also cause contamination of surrounding groundwaters in many instances. However, dewatering underground mine sites can cause problems in regard to treatment and disposal of the removed water, and oxidation of in situ minerals and metals which become exposed to atmospheric air after the dewatering process. Accordingly, abandoned mine workings themselves can comprise environmental hazards and hazards to the personal safety of individuals present in the vicinity of the mineworks.
The problems associated with removing mine tailings and similar materials from stream beds, pits, ponds or tailings piles and the problems associated with reducing the risks to personal safety and the environment from abandoned mine workings have heretofore remained largely unsolved. However, in accordance with the present invention these problems can be substantially overcome.